The present invention relates generally to ruminant nutrition and, more specifically, to the use of a mixture of enzymes in ruminant nutrition to improve the nutritive value of ruminant feedstuffs.
The stomach of ruminants is composed of four chambers: rumen, reticulum, omasum and abomasum. Among these four compartments, the rumen is the most important because most of the nutrients are digested in this chamber. The rumen is sacculated into dorsal, ventral, caudodosal, and caudoventral sacs. The sacculation increases the surface area for efficient absorption. Digestion in the rumen is a fermentation process, providing an anaerobic environment, constant temperature and pH, and good mixing. The fermentation process is accomplished by a profound culture of bacteria, each of which plays a different role in digestion, such as cellulolysis, hemicellulolysis, proteolysis, acid production, methane production, vitamin synthesis, etc. The products from fermentation are either absorbed in the rumen itself or flow out for further digestion and absorption downstream. In addition to the rumen, the abomasum is another important compartment. The abomasum is a “true stomach” which is very similar to the stomach in monogastric animals. It secretes acid to maintain acidic environment. Different from the stomach in monogastric animals, the abomasum secretes lysozyme and therefore is capable of digesting bacteria.
The diet of ruminants typically consists of concentrate and roughage. Roughage usually refers to forage and silage. Forage refers to grasses, legumes, browseable trees and fibrous crop byproducts. Major nutrients in this diet include starch, fiber, protein, fat and oil. Starch is usually degraded either in the rumen or in the abomasum, while fiber, protein, and fat/oil are generally degraded in the rumen by ruminal bacteria. Fiber is digested by cellulolytic and hemicellulolytic bacteria and turned into volatile fatty acids (VFA). Protein either bypasses the rumen or is degraded by proteolytic bacteria and converted into microbial protein which ultimately is utilized by the abomasum. Fat/oil is converted by lipase to fatty acids which are absorbed by the ruminal wall.
As a major component of a typical ruminant diet, forage usually refers to grasses, legumes and fibrous crop byproducts such as rice straw and corn straw. The efficiency of converting forages to productivity is limited by the digestibility of forage cell walls. Plant cell walls usually account for 40-70% of the dry matter of typical forages and, even under ideal conditions, cell wall digestibility in the total digestive tract is generally still less than 65%. Therefore, forage digestibility becomes the bottleneck for the energy availability and causes animals fail to achieve optimal productivity. To make things worse, due to the shortage of high-quality forage, low quality forage is often used to feed ruminants. Because the low quality forage has very little nutritional value, the productivity of ruminant livestock is further limited.
In recent years there have been several attempts to improve the digestibility of forage. A limited number of ruminant enzymes products are commercially available. Many of these enzyme products were merely derivatives of monogastric counterparts, while others manifest unpredictable efficiency. However, researchers have not been successful at using enzymes to enhance the utilization of ruminant diets, partially because of the perceptions that the hydrolytic capacity of the rumen could not be enhanced by supplemental enzymes, and the concerns that such enzymes would be ineffective due to ruminal proteolysis. These misconceptions have been disproved by some recent studies. A couple of researches have shown that adding exogenous fibrolytic enzymes to ruminant diets increased milk production (Schingoethe et al., 1999; Kung et al., 2000) and average daily gain (ADG) (McAllister et al., 1999) in some cases. These cases of improved animal performance were due to the increased feed digestion. Numerous studies have reported increased digestion of dry matter (DM) and fiber measured by in situ and in vitro methods (Beauchemin et al., 2000; Kung et al., 2000).
However, cellulase and xylanase alone are not sufficient to exert the best potential for ruminants. Some other factors, including beta-glucanase, pectinase, mannanase and alpha-galactosidase can be limiting factors. Therefore, it is very important to include these enzymes to release the energy in cell wall of plants.
Some companies advertise their products as dairy specific or ruminant specific. However, these products have two flaws. Firstly, almost all of their products contain amylase. As other animals, ruminants require glucose for normal physiological functions. Starch is usually metabolized either into volatile fatty acid in rumen or into glucose in abmason. If starch is digested too fast in the rumen and leave very little starch for the abmason to generate glucose, ruminants may have insufficient glucose to meet normal biological requirements. Therefore, it is preferable that starch bypass the rumen and be digested in the abmason. For this reason, amylase should not be contained in the feed additive for ruminants. As a matter of fact, some farmers even use amylase inhibitor to help starch to bypass the rumen. Moreover, inclusion of amylase in the rumen additive may cause acidosis. Secondly, these products do not have a complete enzyme profile. There is a need for a product that contains beta-glucanase, pectinase, mannanase and alpha galactosidase, in addition to xylanase and cellulase which are well known as enzyme additives for ruminants. Ruminants consume a lot of legume and grass, so these enzymes are important for ideal digestibility. However, these enzymes are missing in the current products on the market.
Therefore, there is a need for an enzyme product that improves the digestibility of fiber on the basis of most common ruminant diets.